The overall purpose is to develop applications of stable isotopes (13C, 15N, 2H as probes in biochemical systems with the application of appropriate techniques (NMR, GC-MS). In order to accomplish this objective the synthesis of molecules containing these isotopes enriched at selected positions is undertaken, notable synthesis of peptides containing 13C and 15N enriched amino acids. Carbon-13 or nitrogen-15 NMR is used to study the structure and function in solution of such peptides, and proteins derived from them, utilizing the special advantages that such enrichment provides. Selectively deuterium-labelled molecules are also prepared to take advantage of the special properties of this isotope.